The present invention relates to a synthetic resin base plate which accommodates busbars which are press punched and thereafter shear cut, and more particularly to a busbar which takes it into consideration that a resin case is prevented from being scratched by burrs produced at a portion of the busbar where it is shear cut and a construction of a synthetic resin base plate which accommodates the busbar.
In recent years, electric vehicles and hybrid cars have attracted people's attention as environment-friendly motor vehicles which will or are replacing motor vehicles run by gasoline and diesel engines. However, since electric vehicles and hybrid cars require a power supply of high voltage and high output, many batteries are required. In order for such many batteries to be used on electric vehicles and hybrid cars, a whole battery assembly needs to be small in size and hence, battery assembling techniques have become important.
A battery assembly described in Patent Document 1 is known as a related-art battery assembly.
In FIG. 6, a battery assembly 60 is made up of a large number of small planar batteries 61 which are aligned side by side. Each planar battery 61 has bolts functioning as a positive pole 62 and a negative pole 63 which are provided on front and rear end faces, respectively, so as to project therefrom. When disposed side by side, the planar batteries 61 are stacked together so that signs of electrodes of the adjacent planar batteries 61 become opposite, and the whole batteries are fastened to be fixed together by a belt.
In the battery assembly 60 in which the planar batteries 61 are disposed in the way described above, a negative terminal 63 of a first endmost planar battery 61 (a leftmost planar battery 61 in FIG. 6) and a positive terminal 62 of a second planar battery 61, which lies adjacent to the first endmost one, are connected together by a two-hole busbar 81 (refer to FIG. 7A) which is made of a thin, conductive, metallic plate. Similarly, a negative terminal 63 of a third planar battery 61 and a positive terminal 62 of a fourth planar battery 61 are connected together by a two-hole busbar 82 (refer to FIG. 7A). Similarly, a negative terminal 63 of a fifth planar battery 61 and a positive terminal 62 of a sixth planar terminal 61 are connected by a two-hole busbar 83 (refer to FIG. 7A). In this way, when a negative terminal 63 of a thirteenth planar battery 61 and a positive terminal 62 of a fourteenth planar battery 61 in FIG. 7A are then connected by a two-hole busbar 87 (refer to FIG. 7A), the positive terminals 62 and the negative terminals 63 on a far side of the battery assembly 60 (FIG. 6) are all connected to each other.
Here, the “two-hole busbars” will be described.
In FIG. 7A, the two-hole busbars are denoted by reference numerals 81 to 87 and constitute plate for connecting the bolts 62, 63 which are provided on the planar battery 61 (FIG. 6) with the bolts 62, 63 which are provided on the adjacent planar battery 61. The two-hole busbars 81 to 87 are each made of a thin, rectangular, conductive, metallic plate in which two holes are opened in proximity to a central portion thereof. Consequently, an interval between the two holes equals an interval defined between the positive electrode 62 and the negative electrode 63 of the planar batteries which lie adjacent to each other. The bolts 62, 63 are inserted through the corresponding holes, and thereafter, nuts N are fastened on the corresponding bolts 62, 63.
A synthetic resin base plate 101 is obtained through insert molding with the two-hole busbars 81 to 87 inserted in a resin which are disposed to be aligned into a line as is shown in FIG. 7A. By using the synthetic resin base plate 101 so molded, a large number of terminals can be connected easily and quickly.
A battery connection board 100 is made up of the synthetic resin base plate 101 and a cover 103 which is attached to an upper edge of the synthetic resin base plate 101 via a plurality of hinges 102 so as to be opened and closed freely. A portion of the battery connection board 100 shown in FIG. 6 is a rear side of the battery connection board 100 shown in FIG. 7A.
When connecting terminals of the battery assembly 60 on a near side thereof in FIG. 6, the terminals of the planar batteries 61 which are disposed at both end portions of the battery assembly 60 are not connected, respectively, with the terminals of the planar batteries 61 which lie adjacent to the planar batteries at the end portions. Thus, the connection of the terminals on the other side of the battery assembly 60 differs from the connection of the terminals on the one side in which the terminals are connected only by the two-hole busbars in that one-hole busbars are used. The terminals of the planar batteries 61 excluding those disposed at the end portions of the battery assembly 60 are connected by two-hole busbars as in the way described above. Consequently, a busbar 80′ (refer to FIG. 7B) having a hole 80L′ is connected to a positive terminal 62 of the first endmost planar battery 61. Then, a negative terminal 63 of the second planar battery 61, which lies adjacent to the first endmost one, and a positive terminal 62 of the third planar battery 61, which lies adjacent to the second one, are connected by a two-hole busbar 81 (refer to FIG. 7B). Similarly, a negative terminal 63 of the fourth planar battery 61 and a positive terminal 62 of the fifth planar battery 61 are connected by a two-hole busbar 82 (refer to FIG. 7B). In this way, when a busbar 80′ (refer to FIG. 7B) having a hole 80L′ is connected to a negative terminal 63 of the fourteenth planar battery 61 in FIG. 7B, the whole planar batteries 61 of the battery assembly 60 (FIG. 6) are connected in series between the positive terminal 62 and the negative terminal 63 which are individually connected by the busbars 80′ having one hole 80L′.
A synthetic resin base plate 101′ is obtained through insert molding with the one-hole busbar 80′, the two-hole busbars 81 to 86 and the one-hole busbar 80′ inserted in a resin which are disposed to be aligned into a line as is shown in FIG. 7B. By using the synthetic resin base plate 101′ so molded singly, a large number of terminals can be connected easily and quickly.
A battery connection board 100 is made up of the synthetic resin base plate 101′ and a cover 103′ which is attached to an upper edge of the synthetic resin base plate 101′ via a plurality of hinges 102′ so as to be opened and closed freely. A portion of the battery connection board 100′ shown in FIG. 6 is the same side of the battery connection board 100′ shown in FIG. 7B.
The synthetic resin base plate 101 and the synthetic resin base plate 101′ are fixed individually to the bolts 62, 63 on the front and rear end faces of the battery assembly 60, and thereafter the covers 103, 103′ are bent individually through 90 degrees via the pluralities of hinges 102, 102′ which are situated on the upper edges thereof. Then, locking portions K, K′ thereof are brought into abutment with each other, whereby a cover is completed by causing both the locking portions K, K′ to be fixed to each other.
Since the synthetic resin base plates 101, 101′ described in Patent Document 1 are made of a resin through insert molding, the design of a mold becomes complex, and some skills are required when the mold so designed is used. This also requires time and labor hours, and hence, the production costs are increased. In addition, a failure at one portion deteriorates a whole base plate, and this causes a problem of a bad yield.    [Patent Document 1] Japanese Patent Publication Number 2000-149909 A
Then, the applicant of the subject patent application devised a method for fabricating easily a synthetic resin base plate having the same shape and function as those of the synthetic resin base plate 101 without using insert molding. Hereinafter, regarding now this fabrication method as a conventional art, the fabrication method will be described by use of FIGS. 8 to 10.
FIG. 8 shows diagrams illustrating a fabrication process of two-hole busbars. In FIG. 8, shows perspective views of a thin conductive metallic plate in steps 8a to 8d. In the step 8a, the thin conductive metallic plate is used in fabricating busbars. In the step 8a, the thin conductive metallic plate is in which bolt insertion holes are opened in a first press punching. In the step 8a, series of chain-like connected busbars are made in a second press punching. In the step 8d, the series of chain-like connected busbars are shear cut and resulting individual busbars are stacked one on top of the other.
A holed thin conductive metallic plate 80P is prepared by opening bolt insertion holes 81L, 81L at the step 8b in a thin conductive metallic plate 80G at the step 8a in a first press punching. The bolts 62, 63, which are the terminals of the planar batteries 61 of the battery assembly 60 (FIG. 6), are inserted through these bolt insertion holes 81L finally and nuts are individually fastened on the corresponding bolts.
By a second press punching being applied to the holed thin conductive metallic plate 80P, a series of chain-like connected busbars 80 at the step 8c is obtained. Although a series of four connected busbars 81 to 84 is shown in the figure, in reality, a number of busbars 80 are connected to front- and rear-end busbars in a chain-like fashion. The holed thin conductive metallic plate 80P is press punched so as to leave connecting portions 82K to 84K so that the series of chain-like connected busbars 80 results. These connecting portions 82K to 84K constitute shear cutting portions 82S to 84S where the series of chain-like connected busbars 80 is finally shear cut by a shearing machine so as to be separated from each other. Then, the individual busbars are transferred to a busbar feeding position (at [1] in FIG. 9) in a resin case transfer section in a subsequent resin case transfer step in such a state that the individual busbars are sequentially stacked one on top of the other.
FIG. 9 shows, at [1] to [3], diagrams illustrating an order in which the busbars are sequentially accommodated in a resin case in the order of [1] to [3]. At each of [1] to [3], (a) is a perspective view showing a stack of busbars which are shear cut at the shear cutting portions and are then stacked one on top of the other as being situated above the busbar feeding position in the resin case transfer step, and (b) is a perspective view showing a resin case 20 transferred in the resin case transfer section.
The busbars, which are sequentially shear cut by the shearing machine in the separate step and are then stacked one on top of the other, are transferred to the resin case transfer step for accommodation in a resin case to thereby be placed above the busbar feeding position in the transfer section. In the resin case transfer step, a resin case 90 is transferred in a horizontal direction, and when a resin case 91 at a leading end of the resin case 90 reaches right below the busbar feeding position, a busbar 81 is caused to fall from the busbar feeding position into the resin case 91 as is shown at [2] in FIG. 9 for accommodation.
A recess portion 91K is formed in a center of a leading end of the resin case 91 in a direction in which the resin case 91 is transferred, and the connecting portion 81K of the busbar 81 is designed to fit in the recess portion 91K. Therefore, when the connecting portion 81K at a leading end of the busbar 81 which has fallen into the resin case 91 fits in the recess portion 91K, the busbar 81 is allowed to be pushed downwards while being kept horizontal by being so positioned by the fitment of the connecting portion 81K in the recess portion 91K. Then, the busbar 81 is brought into abutment with a stopper formed in a desired position within the resin case 91, whereupon the accommodation of the busbar 81 in the resin case 91 is completed as is shown at [3] in FIG. 9.
Next, in accommodating a subsequent busbar 82 in a subsequent resin case 92, the accommodation is implemented in the same way as described above. Namely, when the subsequent busbar 82 reaches right below the busbar feeding portion, the busbar 82 is caused to fall from the busbar feeding position into the resin case 92 for accommodation as is shown at [3] in FIG. 9. A recess portion 92K is also formed in a center of a leading end of the resin case 92 in a direction in which the resin case 92 is transferred and a connecting portion 82K of the busbar 82 is designed to fit in the recess portion 92K. Therefore, when the connecting portion 82K at a leading end of the busbar 82 which has fallen into the resin case 92 fits in the recess portion 92K, the busbar 82 is allowed to be pushed downwards while being kept horizontal by being so positioned by the fitment of the connecting portion 82K in the recess portion 92K. Then, the busbar 82 is brought into abutment with a stopper formed in a desired position within the resin case 92, whereupon the busbar 82 is accommodated finally in the resin case 92 as is shown at [4] in FIG. 10.
The accommodation of the busbars is implemented in the same way as described above. Namely, at [4] in FIG. 10, when a subsequent resin case 93 reaches right below the busbar feeding position, a busbar 83 is caused to fall into the resin case 93 for accommodation as shown at [4] in FIG. 10. When a connecting portion 83K at a leading end of the busbar 83 fits in a recess portion 93K formed in the resin case 93, the busbar 83 is allowed to be pushed downwards while being kept horizontal by being so positioned by the fitment of the connecting portion 83K in the recess portion 93K. Then, the busbar 83 is brought into abutment with a stopper formed in a desired position within the resin case 93, whereupon the busbar 83 is accommodated finally in the resin case 93 as is shown at [5] in FIG. 10.
Similarly, at [5] in FIG. 10, when a subsequent resin case 94 reaches right below the busbar feeding position, a busbar 84 is caused to fall into the resin case 94 for accommodation as shown at [5] in FIG. 10. When a connecting portion 84K at a leading end of the busbar 84 fits in a recess portion 94K formed in the resin case 94, the busbar 84 is allowed to be pushed downwards while being kept horizontal by being so positioned by the fitment of the connecting portion 84K in the recess portion 94K. Then, the busbar 84 is brought into abutment with a stopper formed in a desired position within the resin case 94, whereupon the busbar 84 is accommodated finally in the resin case 94 as is shown at [6] in FIG. 10.
In this way, all the busbars 81 to 84 shown are individually positioned accurately within the corresponding rein cases 91 to 94 for accommodation, whereby the synthetic resin base plate 101 (FIGS. 7, 8) is obtained through press punching and shear cutting without relying upon insert molding.
According to the approach of the conventional art in which the busbars are accommodated in the resin cases through press punching and shear cutting, the synthetic resin base plate can be fabricated without requiring any special skills compared with the approach utilizing insert molding which is described in Patent Document 1. In addition, the approach of the conventional art requires fewer labor hours and less time, and therefore, the fabrication costs can be reduced.
Various experiments were carried out by using the synthetic resin base plate 101 obtained according to the approach of the conventional art as shown in FIG. 6 to find the fact that a conduction failure occurred from time to time at the terminals of the synthetic resin base plate.
Then, investigations were carried out for a cause for the occurrence of such an conduction failure at the terminals of the synthetic resin base plate which was obtained through press punching and shear cutting according to the conventional art, as a result of which the applicant of the present invention found out that the conduction failure was caused by the following reasons.
In FIG. 11A, a shearing machine 120 includes a lower blade 120B which is formed at a corner of a table 120T and an upper blade 120C which is caused to descend along the lower blade 120B. A shearing target material is placed so that a shearing portion thereof is positioned to be aligned with the lower blade 120B at the corner of the table 120T, and the upper blade 120C is then caused to descend so as to shear cut the shearing target material.
Then, the series of connected busbars 81 to 84 at a process 8c which is obtained as a result of the second press punching according to the conventional art is placed on the table 120T of the shearing machine 120 ([1] of FIG. 11A). Firstly, a leading end portion 80S of the busbar 81 is shorn ([2] of FIG. 11A). Following this, the series of connected busbars 81 to 84 is caused to slide in a traveling direction so that a searing portion 81S is positioned to be aligned with the lower blade 120B at the corner of the table 120T ([3] of FIG. 11A) for implementing shearing ([4] of FIG. 11A). By this action, the busbar 81 is shear cut as is shown at [2] in FIG. 9 to thereby be separated from the remaining connected busbars to fall.
FIG. 11B is a vertical sectional view of the busbar 81 that is obtained in the way described above.
According to FIG. 11B, since shearing is implemented downwards by the upper blade 120C which descends, a burr B is generated in a lower position of a shorn portion of the busbar 81 at a leading end in the traveling direction, and in contrast, a shear drop D is formed in a lower position of the shorn portion. By the same principle, a burr B is generated in an upper position of a shorn portion of the busbar 81 at a rear end in the traveling direction, and in contrast, a shear drop D is formed in a lower position of the shorn portion.
The recess portion 91K is formed in the center of the leading end of the resin case 91 in the direction in which the busbar 81 is transferred and the connecting portion 81K of the busbar 81 is designed to fit in the recess portion 91K for positioning thereof. Consequently, in order for the positioning of the busbar 81 to be implemented properly, the connecting portion 81K needs to fit in the recess portion 91K to such an extent that the connecting portion 81K lightly contacts the recess portion 91K.
By doing so, when the busbar 81 is accommodated within the resin case 91, as is shown at [1] in FIG. 12B, since the burr B is generated in the lower position of the shorn portion of the busbar 81 at the leading end in the traveling direction thereof, in the event that the busbar 81 is placed in the resin case 91 and then continues to be pushed downwards as it is, should there be a design error on at least either the busbar 81 or the resin case 91, the burrs B at the leading end of the busbar 81 scratches a wall surface of the resin case 91, leading to a risk that burr-scratched resin powder BP is produced to fall or scatter.
Thus, there has been a risk that the burr-scratched resin powder BP produced in the way described above enters a fastening portion between the busbar 81 and the battery to cause a conduction failure. Consequently, in order to prevent the occurrence of such a conduction failure, a person performing this busbar accommodating operation has been required to pay much attention in adjusting the position of the busbar 81 so that the busbar 81 does not contact the wall surface of the resin case 91.
Thus, as has been described heretofore, in the busbars according to the conventional art, in accommodating the resin busbar plates in the busbar accommodating portions, the positioning of the busbar is implemented at confronting straight-line portions of the busbar in a minor diameter direction and at apex portions thereof in a major diameter direction of an elliptical shape of the busbar or at the shorn portions of the busbar. Since the series of chain-like connected busbars is shorn one by one, burrs and shear drops are generated on the opposite sides of the shorn portions at both the ends of the individual busbars so shorn. In inserting the busbar into the busbar accommodating portion, a wall surface of the busbar accommodating portion is scratched by the burr which projects towards the busbar accommodating portion, whereby there has been caused a fear that resin scratched off the wall surface causes an conduction failure or a fear that the battery is heated by such an conduction failure.